‘Extreme’ fall in Antarctic sea ice since 2014

Satellite data shows Antarctica has seen an ‘extreme’ fall in expanding sea ice since 2014, more than ever before.

The quantity of ice lost during the last 34 years in the Arctic is the same as that lost in the last 4 years. The actual cause is yet unknown but time will say whether ice will recover or continue its rapid decline.

Though sea ice melting does not affect sea level rise unlike the land ice sheet melting, it will affect the environment by increasing temperature. Vast areas of ice work as a mirror which reflects sunlight and saves the earth from getting warmer. But if sea ice melts, deep ocean water will absorb the sunlight and bring a high heatwave to the surface.

During 40 years of measurements, Antarctic sea ice has been increasing slowly and reached a record maximum in 2014. But since then sea ice extent has decreased, reaching a record low in 2017.

Claire Parkinson, from Nasa’s Goddard Space Flight Center in the US, said: “There has been a huge decrease…it raises the question of why [has it happened], and are we going to see some huge acceleration in the rate of decrease in the Arctic? Only the continued record will let us know.”

In her study, published in the journal Proceedings of the National Academy of Sciences, she called the decline precipitous and a dramatic reversal.

“The Arctic has become a poster child for global warming but the recent sea ice falls in Antarctica have been far worse”, added Parkinson. She has tracked Antarctic sea ice for more than 40 years. She also said, “All of us scientists were thinking eventually global warming is going to catch up in the Antarctic.”

Prof Andrew Shepherd at Leeds University in the UK said: “The rapid decline has caught us by surprise and changes the picture completely. Now sea ice is retreating in both hemispheres and that presents a challenge because it could mean further warming.”

The new research mixed microwave satellite data from 1979 to 2018, to provide excellent measurements of sea ice as the different signals from ocean and ice are very distinct and microwaves can be detected day or night and usually through clouds.

Parkinson used annual averages to connect the long term trends as sea ice expands in winter and recoils in summer every year. She said: “Rates of decline after 2014 were three times faster than the most rapid melting ever recorded in the Arctic. Sea ice extent had a small uptick in 2018, but in 2019 so far there had been a further reduction”.

“As a Nasa scientist, my key responsibility is to get the satellite data out and I hope others will take this 40-year record and try to figure out how these dramatically rapid decreases since 2014 can be explained,” she added.

> Dipto Paul



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